Study On The Pollution Characteristics Of Waterlogging Ponds And The Synergistic Remediation Efficiency Of Aquatic Plant And Microorganisms In Guanzhong Area

Waterlogging ponds are an extremely important small-scale water storage project constructed in arid areas of the north to fully retain surface runoff,mainly distributed in the northwest Loess Plateau region.The waterlogging pond can slow down the runoff from the tableland to the gullies,play a role in consolidating the gullies and protecting the tableland to reduce soil erosion,and also provide a rare wetland ecological landscape for the local area.The pollution problem of rural waterlogging ponds has become a weakness in the rural water environment.Building a"ecologically livable"beautiful countryside and comprehensively promoting the governance of rural waterlogging ponds’water environment are important measures to continuously promote the improvement of rural living environment during the"14th Five Year Plan"period,which is of great significance for implementing the rural revitalization strategy in the new era.Therefore,in response to the current situation of reduced number,loss of function,and environmental pollution in waterlogging ponds,it is required that we understand the fundamental causes and changing patterns of water deterioration in waterlogging ponds,and adopt energy-saving,effective,and eco-friendly water restoration measures to carry out water eutrophication and purification work according to local conditions.In this study,waterlogging ponds in Guanzhong area were selected as the research object.Through field research,basic data such as current waterlogging pond pollution characteristics and water pollution status were obtained.Single plant measures,single microbial measures and plant microbial joint treatment measures were taken to conduct simulation tests.By detecting the content of aquatic plant,test water bodies and sediment related indicators,the remediation efficiency of different treatment measures on test water bodies was studied.The main conclusions are as follows:（1）The sensory status of the water bodies in the study area’s waterlogging ponds is greatly affected by their purification facilities,pollution sources,catchment sources,and management and protection levels.The overall water quality shows characteristics of high nitrogen and high COD.80%of the sampling points have waterlogging ponds with water pollution status above moderate,which cannot meet the water use standards for agriculture and general landscapes.In nitrogen and phosphorus pollution,nitrogen nutrients are the main factor of water pollution,with a contribution rate of 31.17%.The serious nitrogen and phosphorus pollution caused by waterlogging ponds is related to the low self purification capacity of the water bodies,agricultural non-point source pollution caused by excessive use of fertilizers and pesticides in agricultural production activities,and the arbitrary discharge of domestic sewage by residents.Eutrophication of the water bodies will greatly promote the growth and outbreak of algae,laying hidden dangers for the black and foul smell of the water bodies.（2）Aquatic plants can reduce the content of carbon,nitrogen and phosphorus in the water body,improve the water quality of the overlying water body of the waterlogging pond,and play an obvious degradation effect on the organic matter and nitrogen and phosphorus in the sediment.Under the treatment of single plant measure,the biomass of canna increased significantly,the adaptability to the water polluted by waterlogging pond was better and faster,and the absorption of nutrients in the water was stronger.Under the single microbial measure,when the amount of bacteria added exceeds a certain concentration,the excessive amount of bacteria will produce antagonistic competition,which will affect the water quality remediation effect.Therefore,it is not possible to simply increase the amount of bacteria added to achieve better remediation effect.When the dosage of denitrifying agent is 1mg/L,the treatment effect of COD,TN,NH₄⁺-N,TP and other physical and chemical indicators of the test water is the best,and the removal rate is 71.5%,84%,89.3%and 73.3%respectively,and the physical and chemical indicators of the sediment are also significantly improved.（3）The plant rhizosphere environment is complex,and aerobic,anoxic and anaerobic environments can occur around its roots at the same time,which can create the necessary conditions and space for the life activities of rhizosphere microorganisms.At the same time,microorganisms promote the decomposition of organic pollutants,effectively improve the absorption and utilization efficiency of plant roots for nitrogen and phosphorus nutrients in water,and greatly improve the effect of plant-microorganism joint remediation.Under the plant-microorganism combined remediation treatment,the water quality improvement effect is significant.The index values of PH,COD,TN,NH₄⁺-N and TP in the water body of each treatment group are rapidly decreasing,and finally reach a lower concentration value.The water quality meets the Class IV standard of surface water.（4）On the whole,under the test conditions,when the dosage of denitrification bacteria is in the range of 0.5～1mg/L,the combination of canna and canna is the best for the treatment of physical and chemical indicators such as nitrogen and phosphorus in the test water and sediment.In addition,when selecting plant varieties,the adaptability of different plants to specific environmental growth conditions should be taken into account,and factors such as their biomass,subsequent treatment,or resource utilization should be fully considered before making the selection.